Apparatus and methods for treating hardened vascular lesions

ABSTRACT

An angioplasty catheter has a catheter body having a balloon or other radially expandable shell at its distal end. A non-axial external structure is carried over the shell and scores a stenosed region in a blood vessel when the balloon is inflated therein. The catheter has an attachment structure disposed between the catheter body and the balloon to accommodate foreshortening and rotation of the external structure as the balloon is expanded. The external structure may be part of a helical cage structure which floats over the balloon.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/275,264, filed on May 12, 2014, now U.S. Pat. No. 9,962,529 issued onMay 8, 2018, which is a continuation of U.S. patent application Ser. No.13/841,755, filed on Mar. 15, 2013, now U.S. Pat. No. 8,721,667 issuedon May 13, 2014, which is a divisional of U.S. patent application Ser.No. 13/292,716, filed on Nov. 9, 2011, now U.S. Pat. No. 8,454,636issued on Jun. 4, 2013, which is a continuation of U.S. patentapplication Ser. No. 10/917,917, filed on Aug. 13, 2004, now U.S. Pat.No. 8,080,026 issued on Dec. 20, 2011, which is a continuation-in-partof commonly assigned U.S. patent application Ser. No. 10/810,330, filedon Mar. 25, 2004, now U.S. Pat. No. 7,955,350 issued on May 18, 2011,which is a continuation-in-part of U.S. patent application Ser. No.10/631,499, filed on Jul. 30, 2003, now U.S. Pat. No. 7,686,824, issuedon Mar. 30, 2010, which claims the benefit under 35 USC § 119(e) of U.S.Provisional Application No. 60/442,161, filed on Jan. 21, 2003, the fulldisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the field of medical devices, morespecifically to medical devices intended to treat stenoses in thevascular system.

Balloon dilatation (angioplasty) is a common medical procedure mainlydirected at revascularization of stenotic vessels by inserting acatheter having a dilatation balloon through the vascular system. Theballoon is inflated inside a stenosed region in a blood vessel in orderto apply radial pressure to the inner wall of the vessel and widen thestenosed region to enable better blood flow.

In many cases, the balloon dilatation procedure is immediately followedby a stenting procedure where a stent is placed to maintain vesselpatency following the angioplasty. Failure of the angioplasty balloon toproperly widen the stenotic vessel, however, may result in improperpositioning of the stent in the blood vessel. If a drug-eluting stent isused, its effectiveness may be impaired by such improper positioning andthe resulting restenosis rate may be higher. This is a result of severalfactors, including the presence of gaps between the stent and the vesselwall, calcified areas that were not treated properly by the balloon, andothers.

Conventional balloon angioplasty suffers from a number of othershortcomings as well. In some cases the balloon dilatation procedurecauses damage to the blood vessel due to aggressive balloon inflationthat may stretch the diseased vessel beyond its elastic limits. Suchover inflation may damage the vessel wall and lead to restenosis of thesection that was stretched by the balloon. In other cases, slippage ofthe balloon during the dilatation procedure may occur. This may resultin injury to the vessel wall surrounding the treated lesion. Oneprocedure in which slippage is likely to happen is during treatment ofin-stent restenosis, which at present is difficult to treat byangioplasty balloons. Fibrotic lesions are also hard to treat withconventional balloons, and elastic recoil is usually observed aftertreatment of these lesions. Many long lesions have fibrotic sectionsthat are difficult to treat using angioplasty balloons.

An additional problem associated with balloon angioplasty treatment hasbeen the “watermelon seed effect.” Angioplasty is carried out at veryhigh pressures, typically up to twenty atmospheres or higher, and theradially outward pressure of the balloon can cause axial displacement ofthe balloon in a manner similar to squeezing a watermelon seed with thefingers. Such axial displacement, of course, reduces the effectivenessof balloon dilatation. Another problem with conventional angioplastyballoon design has been deflation of the balloon. Even after theinflation medium is removed from a balloon, the deflated configurationwill have a width greater than the original folded configuration whichwas introduced to the vasculature. Such an increase in profile can makeremoval of the balloon difficult.

Atherectomy/Thrombectomy devices intended to remove plaque/thrombusmaterial may also include a structure that expands in a lesion while theplaque/thrombus removal mechanism is within this structure. The removedmaterial is either being stacked in the catheter or sucked out thru thecatheter. When the procedure is done, the expandable structure iscollapsed and the catheter removed. Foreign object removal devicesusually include a basket structure that needs to be expanded to collectthe object and then collapse for retrieval. Distal protection devicesusually include a basket structure that support a mesh that needs to beexpanded distal to the treated lesion to collect the loose objects andthen collapse for retrieval.

These devices usually include an elastic metallic material that needs tobe expanded in the vascular system to fulfill its task and afterwardscollapse to a small diameter to facilitate retrieval. The transitionbetween the collapsed (closed) configuration to the expanded (open)configuration can be done in two ways: the structure can be at anormally closed (collapsed) configuration in which force is applied tocause the structure to expand. In this case, the elastic recoil of thestructure will cause it to collapse back to closed configuration whenthe expanding force ceases. The structure may also be at a normally open(expanded) configuration in which a constraining element is forced overit to hold it down for the collapsed configuration (for example aconstraining tube). When this constraining element is removed thestructure is free to expand to the expanded (open) configuration. Thestructure material may also be non elastic. In this case, the structurewill need to be forced to transit between both collapsed and expandedconfigurations.

One problem associated with conventional angioplasty expansion systemsis that the transition between the collapsed and expanded configurationsinvolves significant rotational and axial reaction forces. Thesereaction forces are applied by the structure on the catheter as a resultof the force applied by the catheter to expand or close the structure.Axial reaction forces are created due the foreshortening of thestructure during expansion. Rotational reaction forces (torques) arecreated when a non longitudinal element is forced to expand/collapse.Since the catheters are usually less stiff than the structure, thesereaction forces may cause the structure to not expand or collapseproperly, or cause undesired deformation to the catheter itself.

To overcome at least some of these problems, U.S. Pat. No. 5,320,634describes the addition of cutting blades to the balloon. The blades cancut the lesions as the balloon is inflated. U.S. Pat. No. 5,616,149describes a similar method of attaching sharp cutting edges to theballoon. U.S. Patent Publication 2003/0032973 describes a stent-likestructure having non-axial grips for securing an angioplasty balloonduring inflation. U.S. Pat. No. 6,129,706 describes a balloon catheterhaving bumps on its outer surface. U.S. Pat. No. 6,394,995 describes amethod of reducing the balloon profile to allow crossing of tightlesions. U.S. Patent Publication 2003/0153870 describes a balloonangioplasty catheter having a flexible elongate elements that createlongitudinal channels in a lesion or stenosis.

While the use of angioplasty balloons having cutting blades has provedto be a significant advantage under many circumstances, the presentcutting balloon designs and methods for their use continue to sufferfrom shortcomings. Most commercial cutting balloon designs, includingthose available from INTERVENTIONAL TECHNOLOGIES, INC., of San Diego,Calif., now owned by BOSTON SCIENTIFIC, of Natick, Mass., haverelatively long, axially aligned blades carried on the outer surface ofan angioplasty balloon. Typically, the blades are carried on arelatively rigid base directly attached to the outer balloon surface.The addition of such rigid, elongated blade structures makes the balloonitself quite stiff and limits the ability to introduce the balloonthrough torturous regions of the vasculature, particularly the smallervessels within the coronary vasculature. Moreover, the cutting balloonscan be difficult to deflate and collapse, making removal of the balloonsfrom the vasculature more difficult than with corresponding angioplastyballoons which do not include cutting blades. Additionally, the axiallyoriented cuts imparted by such conventional cutting balloons do notalways provide the improved dilatation and treatment of fibrotic lesionswhich would be desired.

For these reasons, it would be desirable to provide improved cuttingballoon designs and methods for their use. In particular, it would bedesirable to provide cutting balloons which are highly flexible over thelength of the balloon structure, which readily permit deflation andfacilitate removal from the vasculature, and which are effective intreating all forms of vascular stenoses, including but not limited totreatment of highly calcified plaque regions of diseased arteries,treatment of small vessels and/or vessel bifurcations that will not bestented, treatment of ostial lesions, and treatment of in-stentrestenosis (ISR). Moreover, it would be desirable if such balloonstructures and methods for their use could provide for improvedanchoring of the balloon during dilatation of the stenosed region.

It would further be desirable to minimize the reaction forces applied bythe external structure to the catheter, and at the same time be able tocontrol the expansion of the expandable structure. It would also bedesirable to adjust the compliance of the system in a predictable waywithout changing the materials or geometry of the expandable structure.At least some of these objectives will be met with the inventionsdescribed hereinafter.

2. Description of the Background Art

The following U.S. patents and printed publication relate to cuttingballoons and balloon structures: U.S. Pat. Nos. 6,450,988; 6,425,882;6,394,995; 6,355,013; 6,245,040; 6,210,392; 6,190,356; 6,129,706;6,123,718; 5,891,090; 5,797,935; 5,779,698; 5,735,816; 5,624,433;5,616,149; 5,545,132; 5,470,314; 5,320,634; 5,221,261; 5,196,024; andPublished U.S. Patent Application 2003/0032973. Other U.S. patents ofinterest include U.S. Pat. Nos. 6,454,775; 5,100,423; 4,998,539;4,969,458; and 4,921,984.

SUMMARY OF THE INVENTION

The present invention provides improved apparatus and methods for thedilatation of stenosed regions in the vasculature. The stenosed regionswill often include areas of fibrotic, calcified, or otherwise hardenedplaque or other stenotic material of the type which can be difficult todilatate using conventional angioplasty balloons. The methods andapparatus will often find their greatest use in treatment of thearterial vasculature, including but not limited to the coronary arterialvasculature, but may also find use in treatment of the venous and/orperipheral vasculature, treatment of small vessels and/or vesselbifurcations that will not be stented, treatment of ostial lesions, andtreatment of ISR.

In a first aspect of the present invention, a scoring catheter comprisesa catheter body having a proximal end and a distal end, a radiallyexpandable shell (typically an angioplasty balloon) near the distal endof the catheter body, and a non-axial scoring structure carried over theshell. By “non-axial scoring structure,” it is meant that the structurewill be able to score or cut stenotic material within a treated bloodvessel along lines which are generally in a non-axial direction. Forexample, the scoring lines may be helical, serpentine, zig-zag, or maycombine some axial components together with such non-axial components.Usually, the non-axial scoring pattern which is imparted will includescoring segments which, when taken in total, circumscribe at least amajority of and usually the entire inside wall of the blood vessel up toone time, preferably more than one time, usually more than two times,often at least three times, more often at least four, five, six, or moretimes. It is believed that the resulting scoring patterns whichcircumscribe the inner wall of the vessel will provide improved resultsduring subsequent balloon dilatation.

Usually the scoring structure will comprise at least one continuous,i.e., non-broken, scoring element having a length of at least 0.5 cm,more usually at least 1 cm, often at least 2 cm, usually at least 3 cm,and sometimes at least 4 cm or more. Alternatively, the scoringstructure may comprise a plurality of much smaller segments which may bearranged in a helical or other pattern over the balloon, typicallyhaving a length in the range from 0.1 cm to 2 cm, often being 0.5 cm orless, sometimes being 0.3 cm or less.

In order to promote scoring of the blood vessel wall when the underlyingexpandable shell is expanded, the scoring structure will usually have avessel contact area which is 20% or less of the area of the expandableshell, usually being below 10%, and often being in the range from 1% to5% of the area of the expandable shell. The use of a shell having such arelatively small contact area increases the amount of force applied tothe vascular wall through the structure by expansion of the underlyingexpandable shell. The scoring structure can have a variety of particularconfigurations, often being in the form of a wire or slotted tube havinga circular, square, or other cross-sectional geometry. Preferably, thecomponents of the scoring structure will comprise a scoring edge, eitherin the form of a honed blade, a square shoulder, or the like. Apresently preferred scoring edge is electropolished and relativelysmall.

In a preferred embodiment, the scoring structure may be formed as aseparate expandable cage which is positioned over the expandable shellof the catheter. The cage will usually have a collar or other attachmentstructure at each end for placement on the catheter body on either sideof the expandable shell. A collar may be a simple tube, and otherattachment structures will usually be crimpable or otherwisemechanically attachable to the catheter body, such as a serpentine orother ring structure. The attachment structures on the cage may beattached at both ends to the catheter body, but will more usually beattached at only a single end with the other end being allowed to floatfreely. Such freedom allows the scoring structure to shorten as thestructure is expanded on the expandable shell. In certain embodiments,both ends of the scoring structure will be fixed to the catheter body,but at least one of the attachment structures will have a spring orother compliant attachment component which provides an axial extensionas the center of the scoring structure foreshortens.

In many cases, since the scoring elements are non-axial, there aretorques induced during the expansion of the balloon and the shorteningof the scoring structure. These torques may be high, and if one end ofthe scoring structure is constrained from rotation, the scoring elementwill not expand properly. The final expanded configuration of thescoring element is achieved via shortening and rotation.

In a preferred embodiment, both sides of the scoring element are fixedto the catheter, but at least one side will have a compliant structurewhich will provide axial tension and at the same time will allow thescoring element to rotate to its final configuration.

In some cases both ends of the scoring element are fixed and theshortening is achieved by deformation of the wire. For example, the wirecan have a secondary structure which permits elongation (e.g., it may bea coiled filament) or can be formed from a material which permitselongation, e.g., nitinol. The scoring element can be attached in bothends, in a way that will allow rotation. In the case were the torquesare low (depending on the design of the scoring element) there is noneed for rotation and the torque can be absorbed either be the scoringelement or by the catheter.

In all cases, the scoring structure is preferably composed of an elasticmaterial, more preferably a super elastic material, such as nitinol. Thescoring structure is thus elastically expanded over the expandableshell, typically an inflatable balloon similar to a conventionalangioplasty balloon. Upon deflation, the scoring structure willelastically close to its original non-expanded configuration, thushelping to close and contain the balloon or other expandable shell.

In some cases the scoring element will be a combination of more than onematerial. In one case the scoring element can be made from nitinol andparts of it can be made from stainless steel. In other cases the scoringelement can be made of stainless steel or nitinol and part of it can bemade from polymer to allow high deformations.

In other preferred embodiments, the assembly of the shell and thescoring structure will be sufficiently flexible to permit passagethrough tortuous regions of the vasculature, e.g., being capable ofbending at radius of 10 mm or below when advanced through 45°, 90°, orhigher bends in the coronary vasculature. Usually, the scoring structurewill comprise one or more scoring elements, wherein less than 70% of thecumulative length of the scoring element is aligned axially on the shellwhen expanded, preferably being less than 50% of the cumulative length,and more preferably being less than 25% of the cumulative length. Inother instances, the scoring structure may comprise one or more scoringelements, wherein the cumulative length of the scoring element includesa non-axial component of at least 10 mm, preferably at least 12 mm, andmore preferably 36 mm. Preferably, at least some of the scoring elementswill have scoring edges which are oriented radially outwardly along atleast a major portion of their lengths at all times during inflation anddeflation and while inflated. By “radially outward,” it is meant that asharp edge or shoulder of the element will be oriented to score or cutinto the stenotic material or the interior wall of the treated vessel,particularly as the shell is being inflated.

The scoring elements will usually, but not necessarily, have a scoringedge formed over at least a portion of their lengths. A “scoring edge”may comprise a sharpened or honed region, like a knife blade, or asquare shoulder as in scissors or other shearing elements.Alternatively, the scoring elements may be free from defined scoringedges, e.g., having circular or the other non-cutting profiles. Suchcircular scoring elements will concentrate the radially outward force ofthe balloon to cause scoring or other disruption of the plaque or otherstenotic material being treated.

In a second aspect of the present invention, the scoring cathetercomprises a catheter body and a radially expandable shell, generally asset forth above. The scoring structure will be composed of elementswhich circumscribe the radially expandable shell. By “circumscribing theradially expandable shell,” it is meant that at least some scoringelements of the scoring structure will form a continuous peripheral pathabout the exterior of the expandable shell during expansion. An exampleof such a fully circumscribing structure is a helical structure whichcompletes up to one 360° path about the balloon before, during, andafter expansion, usually completing two complete revolutions, andfrequently completing three, four, or more complete revolutions.Exemplary helical structures may include two, three, four, or moreseparate elements, each of which is helically arranged around theradially expandable shell.

In a third aspect of the present invention, a scoring catheter comprisesa catheter body and a radially expandable shell, generally as set forthabove. An elongated scoring structure is carried over the shell, and theassembly of the shell and the scoring structure will be highly flexibleto facilitate introduction over a guide wire, preferably beingsufficiently flexible when unexpanded so that it can be bent at an angleof at least 90°, preferably 180°, at a radius of 1 cm without kinking orotherwise being damaged. Such flexibility can be determined, forexample, by providing a solid cylinder having a radius of 1 cm andconforming the assembly of the scoring structure and expandable shellover the cylinder. Alternatively, the assembly can be advanced over aguide wire or similar element having a 180° one centimeter radius bend.In either case, if the assembly bends without kinking or other damage,it meets the requirement described above. Other specific features inthis further embodiment of the catheters of the present invention are asdescribed above in connection with the prior embodiments.

In a fourth aspect of the present invention, a plaque scoring cathetercomprises a catheter body and a radially expandable balloon, generallyas set forth above. A plurality of scoring elements are distributed overthe balloon, typically being attached directly to an outer surface ofthe balloon. The scoring elements will be relatively short, typicallyhaving lengths below about 25% of the balloon length, preferably havinglengths in the range from 2% to 10% of the balloon length. Therelatively short, segmented scoring elements will permit highly flexibleassemblies of balloon and scoring elements, generally meeting theflexibility requirement set forth above. The scoring elements may bearranged randomly over the balloon but will more usually be distributeduniformly over the balloon. In specific embodiments, the scoringelements may be arranged in helical, serpentine, or other regularpatterns which circumscribe the balloon. As the balloon expands, suchshort segments will generally move apart from each other, but will stillimpart the desired scoring patterns into the vascular wall as theballoon is inflated.

In a fifth embodiment, the scoring catheter according to the presentinvention comprises a catheter body and a radially expandable balloongenerally as set forth above. The balloon has a plurality of lobesextending between ends of the balloons, and at least one scoring elementwill be formed on at least one of the lobes in a manner arranged toscore stenotic material as the balloon is expanded. The lobe willusually be in a helical pattern, and typically two, three, or more lobeswill be provided. In the case of helical lobes, the scoring element(s)will usually be disposed along a helical peak defined by the helicallobe when the balloon is inflated. Such helical scoring elements will bearranged to accommodate balloon inflation, typically being stretchable,segmented, or the like.

In still another aspect of the apparatus of the present invention, anexpandable scoring cage is adapted to be carried over a balloon of aballoon catheter. The scoring cage comprises an assembly of one or moreelongate elastic scoring elements arranged in a non-axial pattern. Asdefined above, the non-axial pattern may comprise both axial andnon-axial segments. The assembly is normally in a radially collapsedconfiguration and is expandable over a balloon to a radially expandedconfiguration. After the balloon is deflated, the assembly returns to aradially collapsed configuration, preferably being assisted by theelastic nature of the scoring cage. Advantageously, the scoring cagewill enhance uniform expansion of the underlying balloon or otherexpandable shell and will inhibit “dog boning” where an angioplastyballoon tends to over inflate at each end, increasing the risk of vesseldissection. The scoring elements will be adapted to score hardenedstenotic material, such as plaque or fibrotic material, when expanded bythe balloon in a blood vessel lumen. The scoring cage may be adapted tomount over the balloon with either or both ends affixed to the balloon,generally as described above in connection with prior embodiments.Preferred geometries for the scoring elements include those whichcircumscribe the balloon, those which are arranged helically over theballoon, those which are arranged in a serpentine pattern over balloonand the like.

In yet another aspect of the present invention, a method for dilatatinga stenosed region in a blood vessel comprises radially expanding a shellwhich carries a scoring structure. The scoring structure scores anddilates the stenosed region and includes one or more non-scoringelements arranged to impart a circumscribing score pattern about theinner wall of the blood vessel as the shell is expanded. The stenosedregion is typically characterized by the presence of calcified plaque,fibrotic plaque, or other hardened stenotic material which is preferablyscored prior to dilatation. Preferably, the scoring structure will notbe moved in an axial direction while engaged against the stenosedregion, and the scoring structure may optionally be free from axiallyscoring elements.

In still another aspect of the present invention, an angioplastycatheter comprises a catheter body and a radially expandable shell nearthe distal end of the catheter body. An external structure, such as ascoring structure or cutting structure, is carried over but unattachedto the shell. The catheter further comprises an attachment structurehaving a proximal end and a distal end attached to the scoringstructure, wherein the attachment structure is sufficiently sized andcompliant to accommodate reaction forces or geometrical changes producedby the scoring structure as it is expanded by the shell. Generally, atleast a portion of said scoring structure is arranged helically over theshell. However, the scoring structure may comprise numerous differentconfigurations as described above.

In one aspect of the present invention, the proximal end of theattachment structure is fixed to the catheter body and the distal end ofthe attachment structure is secured to the proximal end of the scoringstructure. In all cases, the attachment structure is capable axially androtationally extending to accommodate foreshortening of the scoringstructure as the shell is expanded.

In a preferred embodiment, the attachment structure comprises acompliance tube having an outer diameter and an inner diameter thatextends over the catheter body. The inner diameter of the compliancetube is generally larger than an outer diameter of the catheter body sothat the compliance tube freely extends and/or rotates with respect tothe catheter body as the scoring structure foreshortens.

The compliance tube may also be sized to control the compliance of thescoring structure and expandable shell. Generally, the compliance tubehas wall thickness ranging from 0.001 in to 0.1 in., preferably 0.005in. to 0.05 in. The wall thickness may be increased to lessen thecompliance of the system, or decreased to create a greater compliance.The length of the compliance tube may also be adjusted to control thecompliance of the system. Generally, the compliance tube has a lengthranging from 1 cm to 10 cm, but may range up to 30 cm or more forembodiments wherein the tube extends across the length of the catheterbody.

In most cases, the material of the compliance tube may also be selectedto control the compliance of the scoring structure and expandable shell.Generally, the compliance tube comprises an elastic material, preferablya polymer such as nylon or Pebax™. Alternatively, the compliance tubemay comprise a braided material, metal or wire mesh.

In some aspects of the present invention, the compliance tube may haveone or more perforations to control the compliance of the scoringstructure and expandable shell. Generally, the perforations comprise oneor more slots extending along the outside circumference of thecompliance tube. The slots may form a pattern along the outsidecircumference of the compliance tube. The slots may be parallel to eachother and/or extend helically or radially across the circumference ofthe compliance tube. The slots themselves may be formed of a variety ofshapes, such as circular or rectangular.

Preferably, the compliance tube has an outer diameter that tapers fromits distal end to its proximal end so that the outside diameter at theproximal end is slightly larger than the inner diameter, and the outsidediameter at the distal end is sized to approximate the diameter of thescoring structure when in a collapsed configuration. This allows for thecatheter to be readily removed from a vessel without catching orsnagging on the vessel wall. For the tapered configuration, the outerdiameter of the compliance tube will vary depending on the size of thecatheter body and the expansion cage, but the diameter generally tapersdown in the range of 0.004 in. to 0.010 in. from the distal end to theproximal end.

In another aspect of the invention, the attachment structure isconnected at its distal end to the scoring structure and at its proximalend to a manipulator. Typically, the manipulator is positioned at theproximal end of the catheter body and the attachment structure extendsfrom the scoring structure across the length of the catheter body. Inall cases, the attachment structure is capable of axially androtationally extending to accommodate foreshortening of the scoringstructure as the shell is expanded.

In a preferred embodiment, the attachment structure comprises acompliance tube having an outer diameter and an inner diameter thatextends over the catheter body. Typically, the inner diameter of thecompliance tube is larger than an outer diameter of the catheter body sothat the compliance tube freely extends and rotates with respect to thecatheter body as the scoring structure foreshortens. The compliance ofthe scoring structure and expandable shell may be controlled byadjusting the thickness, length, or material selection of the compliancetube.

In some embodiments, the compliance of the scoring structure iscontrolled by actuating the manipulator during expansion or contractionof the radially expandable shell. Specifically, the attachment structuremay be axially advanced with respect to the catheter body as the balloonis being inflated or deflated. For example, the attachment structure maybe pulled away from the distal end of the catheter body while theballoon is being expanded to constrain the compliance of the balloon.Alternatively, the manipulator may be used to rotate the attachmentstructure with respect to the catheter body to control the compliance ofthe balloon during transition.

In another embodiment of the present invention, a method of dilatating astenosed region in a blood vessel comprises introducing a scoringstructure carried over an expandable shell that is connected to acatheter body by an attachment structure, and expanding the scoringstructure within a stenosed region within the blood vessel. In thismethod, the attachment structure axially and/or rotationally extends toaccommodate foreshortening of the scoring structure as the shell isexpanded. The attachment structure generally comprises a compliance tubehaving an outer diameter and an inner diameter that extends over thecatheter body, wherein the inner diameter of the compliance tube islarger than an outer diameter of the catheter body so that thecompliance tube freely extends and rotates with respect to the catheterbody as the scoring structure foreshortens. The thickness, length, andmaterial of the compliance tube may be selected to control thecompliance of the scoring structure and expandable shell.

In some embodiments, the method further comprises the step of fixing theproximal end of the attachment structure to the catheter body.Alternatively, the method may comprise the step of fixing the proximalend of the attachment structure to a manipulator. In such an embodiment,the manipulator is positioned at the proximal end of the catheter bodyand the attachment structure extends from the scoring structure acrossthe length of the catheter body. This allows for the compliance of thescoring structure and balloon to be controlled by actuating themanipulator during expansion or contraction of the radially expandableshell. Actuation of the manipulator may occur by axially advancing,pulling, or rotating the attachment structure with respect to thecatheter body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 1A, 1B, and 1C are schematic illustrations of the balloonscoring structure embodiment in accordance with an embodiment of theinvention.

FIG. 2 is a schematic illustration of an exemplary helical scoringstructure embodiment in accordance with embodiments of the invention.

FIG. 3 is a schematic illustration of an expanded angioplasty ballooncarrying a helical scoring structure in accordance with embodiments ofthe invention.

FIG. 4 illustrates a scoring structure comprising an alternatingserpentine pattern of intermediate scoring elements between a pair ofend collars.

FIG. 5 illustrates the serpentine scoring elements of the embodiment ofFIG. 4 shown in a rolled-out configuration.

FIG. 6 illustrates a scoring structure comprising alternating C-shapedscoring elements between a pair of end collars.

FIG. 7 illustrates the C-shaped scoring elements of the embodiment ofFIG. 6 shown in a rolled-out configuration.

FIG. 8 is a view of one of the C-shaped scoring elements taken alongline 8-8 of FIG. 6.

FIG. 9 illustrates an alternative double C-shaped scoring element whichcould be utilized on a scoring structure similar to that illustrated inFIG. 6.

FIG. 10 illustrates an alternative embodiment of a helical scoringstructure comprising serpentine and zigzag structures for mounting ontoa balloon catheter.

FIG. 11 illustrates a first of the serpentine mounting elements of thescoring structure of FIG. 10.

FIG. 12 illustrates a second of the serpentine mounting elements of thescoring structure of FIG. 10.

FIG. 13 illustrates an alternative mounting structure for a helical orother scoring structure.

FIG. 14 illustrates the mounting structure of FIG. 13 shown in arolled-out configuration.

FIG. 15 shows yet another embodiment of a mounting element for thescoring structures of the present invention.

FIG. 16 illustrates the mounting structure of FIG. 15 shown in arolled-out configuration.

FIG. 17a illustrates yet another alternative embodiment of a catheterconstructed in accordance with the principles of the present invention,where an attachment structure is disposed between the scoring structureand the catheter body.

FIG. 17b illustrates the structure of FIG. 17a shown without theballoon.

FIGS. 18a-c illustrate a catheter constructed in accordance with theprinciples of the present invention having an attachment structure withvarious patterned perforations.

FIG. 19 illustrates another embodiment of a catheter constructed inaccordance with the principles of the present invention having a taperedattachment structure.

FIG. 20 illustrates yet another alternative embodiment of a catheterconstructed in accordance with the principles of the present invention,where an attachment structure is connected to a manipulator.

FIG. 21 illustrates an embodiment of the invention having a laminatedsection at the distal end of the compliance tube.

FIG. 22 illustrates another view of the embodiment of FIG. 21.

FIG. 23 illustrates the embodiment of FIG. 21 with an expandable ballooninserted within the scoring structure.

FIG. 24 illustrates an embodiment with a sleeve over the distal end ofthe scoring structure.

FIG. 25 illustrates a method of the present invention utilizing aninsertion tube to mount the scoring structure over the expandableballoon.

FIG. 26 illustrates shows the insertion tube inserted over theexpandable balloon.

FIG. 27 illustrates a scoring catheter of the present invention with theinsertion tube removed.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionwill be described. For purposes of explanation, specific configurationsand details are set forth in order to provide a thorough understandingof the present invention. However, it will also be apparent to oneskilled in the art that the present invention may be practiced withoutthe specific details presented herein. Furthermore, well-known featuresmay be omitted or simplified in order not to obscure the presentinvention.

Embodiments of the present invention relate to device forrevascularization of stenotic vessels and specifically to a ballooncatheter having external elements. The dilatation device comprises aconventional dilatation balloon such as a polymeric balloon and aspiral, or external elements with other configurations mounted on theballoon catheter.

Reference is now made to FIGS. 1, 1A, and 1B, which are schematicillustrations of a dilatation device 10 in accordance with embodimentsof the invention. The dilatation device 10 includes a dilatation balloon12, which may be any conventional angioplasty balloon such as commonlyused by interventional cardiologists or radiologists, and a helical orspiral unit 14 mounted over or attached to dilatation balloon 12. Thecompliance of the balloon and the scoring element(s) should be chosen toassure uniform expansion of the balloon substantially free from“dog-boning” as the combined structure expands within a lesion. If acompliant or a semi-compliant balloon is used and the compliance of thescoring element was not matched to comply with the properties of theballoon, the expansion of the balloon-scoring element system will not beuniform. This non-uniformity may impair the efficacy of the scoringcatheter and, in some cases, may result in poor performance. Forexample, under given pressure, certain parts of the balloon will be ableto expand while other parts will be constrained by excessive resistanceof the scoring elements.

Helical unit 14 is typically made of nitinol. Helical unit 14 may bemade of other metals such stainless steel, cobalt-chromium alloy,titanium, and the like. Alternatively, spiral unit 14 may be a polymericspiral, or made of another elastic material. Helical unit 14 may beattached at its proximal and distal ends to the proximal end 17 anddistal end 18 of dilatation balloon 12. Alternatively, spiral unit 14may be attached to the distal end and/or the proximal end of dilatationballoon 12 by collar-like attachment elements 15 and 16. Spring or othercompliant elements may be alternatively or additionally provided as partof the attachment elements to accommodate shortening of the helical unitas it is expanded.

Dilatation device 10 is inserted into the vascular system, for example,using a conventional catheter procedure, to a region of stenoticmaterial 22 of blood vessel 20. (The term “stenotic” is used herein torefer to the vascular lesion, e.g., the narrowed portion of the vesselthat the balloon is meant to open.) At the stenotic area, the dilatationballoon 12 is inflated, for example, by liquid flow into the balloon.Helical unit 14 widens on the inflated dilatation balloon 12. Oninflation, the dilatation balloon 12 together with the helical unit 14is pressed against the walls of blood vessel 20 as shown in FIG. 1B.

Reference is now made to FIG. 1C, illustrating blood vessel 20 after thedeflation of dilatation balloon 12. Helical unit 14 narrows whendeflating the dilatation balloon 12, thus the dilatation device 10 isnarrowed and may be readily retrieved from blood vessel 20. Thedeflation profile of the balloon 10 is low and mainly circular. Thestenotic material 22 in blood vessel 20 is pressed against blood vessel20 walls to widen the available lumen and enhance blood flow. Thepressing of helical unit 14 against the walls of blood vessel 20 causesscoring 23 in the stenotic area.

Reference is now made to FIG. 3 that shows a scoring structure in theform of a single wire 24 wrapped around a dilatation balloon 12 in ahelical configuration.

In other embodiments, the scoring structure of the present invention canhave a non-helical configuration. Any design of scoring structure thatcan accommodate an increase in the diameter of the balloon 12 uponinflation, and return to its configuration when the balloon is deflated,is an appropriate design useful in the invention. At least a portion ofthe scoring elements will not be parallel to the longitudinal axis ofthe balloon catheter to enhance flexibility and improve scoring.

Referring again to FIGS. 1A-1C, helical unit 14 is pushed outwardly bythe inflation of the balloon 12, and is stretched by the inflation ofthe balloon. When the balloon is deflated, helical unit 14 assists inthe deflation by its elastic recoil. This active deflation is faster andalso leads to a low profile of the deflated balloon. The balloon 12 isdisposed within the helical unit 14, which returns to its pre-inflatedshape and forces the balloon to gain a low radial profile.

In another embodiment of the invention, dilatation device 10 may carry astent. The stent can be crimped over the helical unit 14. In this way,the helical unit 14 can push the stent against hard areas of the lesion,enabling proper positioning of the stent against the vessel wall, evenin hard-calcified lesions without pre-dilation.

Reference is now made to FIG. 2, illustrating the helical unit 14 inaccordance with embodiments of the invention. Helical unit 14 istypically made of nitinol. Helical unit 14 includes three wires 19 thatare attached to collars 15 and 16 at the proximal end and distal end,respectively. Alternatively the scoring structure may be formed as ametallic cage, which can be made from a slotted tube, or polymeric cageor polymeric external elements. Alternatively, the scoring structure maycomprise wires of other elements attached directly to the balloonmaterial or close to the balloon ends.

Wires 19 (FIG. 2) are attached between collars 15 and 16. The diameterof the wires is typically in the range of 0.05 mm to 0.5 mm.Alternatively, a cage (for example a metallic cage made of a slottedtube) can be used in several configurations that allow local stressconcentrations. The size and shape of the cross section of the cageelements or the cross section of the wires can vary. The cross sectioncan be a circle, rectangle, triangle, or other shape.

In alternative embodiments, the wires 19 may comprise short segmentsthat are attached to the balloon 12.

In further alternative embodiments of the invention, the helical unit 14may be glued, thermally bonded, fused, or mechanically attached at oneor both ends to dilatation balloon 12.

In yet another embodiment, a scoring structure may comprise wires thatare attached to the dilatation balloon 12 in a helical configuration orother configuration. The wires may be thermally attached to the balloon12, glued, mechanically attached, or the like.

In still another embodiment, a scoring structure comprises wire or cageelements that are not parallel to the longitudinal axis of the balloon12 so that the combination of the scoring structure 19 and the balloon12 remains flexible.

In additional embodiments, the combination of dilatation balloon 12 andscoring structure scores the lesion and provides better vesselpreparation for drug eluting stents by allowing better positioning ofthe stent against the vessel wall and diffusion of the drug through thescores in the lesion.

In these embodiments, the balloon can be used as a platform to carrydrugs to the lesion where scoring of the lesion can enhance delivery ofthe drug to the vessel wall.

In these embodiments, the balloon can be used for a local drug deliveryby embedding drug capsules, drug containing polymer, and the like,through the stenotic material and into the vessel wall.

From the above, it can be seen that the invention comprises cathetersand scoring structures, where the scoring structures are positioned overthe balloons or other expandable shells of the catheter. The scoringstructures may be attached directly to the balloons or other shells, insome cases being embedded in the balloon material, but will more usuallybe formed as separate cage structures which are positioned over theballoon and attached to the catheter through attachment elements oneither side of the balloon. The expandable cages may be formed usingconventional medical device fabrication techniques, such as those usedfor fabricating stents, such as laser cutting of hypotube and othertubular structures, EDM forming of hypotubes and tubes, welding of wiresand other components and the like.

Typically, such expandable shell structures will comprise the attachmentelements and an intermediate scoring section between the attachmentelements. As illustrated in the embodiments above, the attachmentelements may be simple cylindrical or tube structures which circumscribethe catheter body on either side of the balloon or other expandableshell. The simple tube structures may float over the catheter body,i.e., be unattached, or may be fixed to the catheter body. A number ofalternative embodiments for the attachment elements will be described inconnection with the embodiments below.

The intermediate scoring sections may also have a variety ofconfigurations where at least some of the scoring elements willtypically be disposed in a non-axial configuration, i.e., in a directionwhich is not parallel to the axial direction of the expandable cage. Apreferred configuration for the intermediate scoring section comprisesone or more helical elements, generally as illustrated in the priorembodiments. Other exemplary configurations are set forth in theembodiments described below.

Referring now in particular to FIGS. 4 and 5, an expandable scoring cage100 comprises first and second attachment elements 102 and 104,respectively, and an intermediate scoring section 106 comprising aplurality of curved serpentine members 110. The serpentine members 110extend circumferentially in opposite directions in an alternatingmanner. This can be understood by observing a “rolled-out” view of theserpentine elements as illustrated in FIG. 5. A second alternativescoring cage structure 120 is illustrated in FIGS. 6-8. The scoring cage120 comprises first and second attachment elements 122 and 124 joined bya spine 126. A plurality of C-shaped scoring elements 128 and 130 areattached to the spine and extend in opposite circumferential directions.The shape of the element can be observed in FIG. 8. The oppositedirections may be observed in the rolled-out view of FIG. 7.

It will be appreciated that a variety of different circumferentialstructures may be used in place of the C-shaped structures of FIGS. 6-8.For example, a pair of opposed C-shaped partial ring structures may beutilized, as illustrated in FIG. 9. The C-shaped structures of FIG. 6 orthe double C-shaped structures of FIG. 9 can also be extended so thatthey wrap around a balloon more than one time, either over or under thespine structure 126.

The expandable cage structures 100 and 120 will each be mounted over adilatation balloon, such as the balloon of FIGS. 1-3, with theattachment elements secured to the catheter body on either side of thedilatation balloon. The tube or cylindrical attachment elements 102,104, 122, and 124 may simply float over the catheter body. In otherembodiments, however, it may be desirable to use an adhesive or othermeans for affixing either one or both of the attachment elements to thecatheter body. Having at least one floating attachment element, however,is often desirable since it can accommodate shortening of theintermediate scoring section as that section radially expands. In othercases, however, the individual scoring elements may possess sufficientelasticity to accommodate such shortening. For example, nitinol andother shape memory alloys possess significant stretchability, typicallyon the order of 8%, which in some instances will be sufficient toaccommodate any tension applied on the intermediate scoring section byradial expansion of the balloon.

Referring now to FIGS. 10-12, alternative attachment elements are shownon an embodiment of an expandable scoring cage 140 comprising threehelical scoring elements 142 which make up the intermediate scoringsection. A first attachment element 146 comprises a single serpentinering, as best illustrated in FIG. 11 while a second attachment element148 comprises a pair of tandem serpentine rings 150 and 152, as bestillustrated in FIG. 12. The use of such serpentine attachment structuresis beneficial since it permits crimping of either or both of thestructures onto the catheter body in order to fix either or both ends ofthe structure thereto. Usually, the single serpentine attachmentstructure 146 will be affixed to the catheter body while the doubleserpentine structure will be left free to allow movement of that end ofthe scoring cage to accommodate radial expansion of the underlyingballoon.

Referring now to FIGS. 13 and 14, a further alternative embodiment of anattachment element useful in the scoring cages of the present inventionis illustrated. Attachment element 180 includes a pair of serpentinerings 182 and 184, generally as shown in FIG. 13, in combination with acoil spring structure 186 located between said rings 182 and 184. Thecoil spring structure 186 includes three nested coil springs 190, eachjoining one of the bend structures 192 and 194 on the serpentine rings182 and 184, respectively. The structure of the spring structure andadjacent serpentine rings can be understood with reference to therolled-out configuration shown in FIG. 14.

The attachment structure 180 is advantageous since it permits a fixedattachment of the outermost ring 182 to the underlying catheter bodywhile the inner ring 184 remains floating and expansion and contractionof the intermediate scoring section, comprising helical elements 196, isaccommodated by the coil spring structure 186. Since the scoring cage isfixed to the catheter, any risk of loss or slippage from the balloon isreduced while sufficient compliance is provided

to easily accommodate radial expansion of the intermediate scoringsection. By attaching the structures 180 at at least one, and preferablyboth ends of the scoring cage, the risk of interference with a stent isreduced.

In some embodiments, collars, such as those shown in FIGS. 1 and 2, orattachment elements, such as those shown in FIGS. 10-12, may comprise aflexible material that allows the collar or attachment element to expandwhile being mounted over the balloon catheter and then be collapsed tothe diameter of the catheter. The expandability of the collars and/orattachment elements may be achieved by a compliant memory material suchas nitinol or a polymer, or by use of a flexible serpentine design asshown in FIGS. 10-12. Where collars are used, the collar may be shapedor have a slit down the circumference (not shown) so that the collar maybe expanded during mounting over the balloon. Alternatively, the collarmay be oversized to accommodate the balloon diameter mounting, and thencrimped down to secure the secure the scoring structure to the catheterbody.

Yet another embodiment of the attachment element of the presentinvention includes an axial spring as shown in FIGS. 15 and 16. Theattachment element 200 includes a terminal serpentine ring 202 and anintermediate spring structure 204 including a number of axial serpentinespring elements 206. The nature of the serpentine ring elements 206 canbe observed in the rolled-out configuration of FIG. 16. Optionally, asecond serpentine ring 210 may be provided between the attachmentstructure 200 and the helical scoring elements of the intermediatescoring section 212.

The embodiments of FIGS. 13-16 comprise spring-like elements 186 and 204to accommodate axial shortening of the scoring structure upon radialexpansion. It will be appreciated that other metal and non-metal axiallyextensible structures could also be used in such attachment structures.For example, elastic polymeric tubes could be attached at one end to thescoring structures and at another end to the catheter body (or to aring, collar or other structure which in turn is fixed to the catheterbody).

Referring now to FIGS. 17a and 17b , a further embodiment of anangioplasty catheter 250 having an axially distensible attachmentstructure 258 is illustrated. External structure 252 is held overexpandable dilatation balloon 254 and is fixed at one end to the distalend 260 of catheter body 256. The external structure may comprise anystructure typically used for removal of plaque/thrombus from a vesselwall such as a scoring structure, cutting structure, or crushingstructure. The proximal end 262 of external structure 252 is connectedto the distal end 264 of attachment structure 258. The proximal end 266of attachment structure 258 is fixed to the catheter body 256. Asdescribed below, the attachment structure 258 may be configured toreduce forces applied on the external structure 252 and the catheterbody 256 during expansion and contraction of balloon 254.

In a preferred embodiment, attachment structure 258 comprises acylindrical over-tube, or compliance tube, made of an elastic material.Over-tube 258 generally has an inner diameter that is slightly greaterthan the outer diameter of the catheter body 256. Because only a smallsection of the proximal end of the attachment structure 258 is fixed tothe catheter body, the distal end 264 attached to external structure 252is free floating, and is free to slide axially and rotationally withrespect to catheter body 256. Attachment structure 252 may be fixed, forexample by adhesion, directly to the catheter body 256 and externalstructure 252, or to a collar or other intermediate attachment means.

As balloon 254 is expanded, external structure 252 expands incircumference and contracts axially along the catheter body 256,creating axial force A on attachment structure 258. Attachment structure258, fixed to the catheter at its end 266, axially stretches toaccommodate the axial movement of the external structure 252. Externalstructure 252 also tends to rotate about the catheter body 256, causinga torsional force T. The distal end 264 of attachment structure 258rotates through the full range of motion of scoring structure 252 toaccommodate torsional force T, while proximal end 266 remains stationarywith respect to catheter body 256.

The configuration illustrated in FIGS. 17a and 17b allows the complianceof the expandable system to be controlled. Generally, where one end ofthe scoring structure is free, the compliance of the expandable systemwill be a combination of the compliance of the balloon and the scoringstructure. However, because the ends of the expandable system shown inFIG. 17 are fixed at distal end 260 and proximal end 266, the attachmentstructure controls the compliance of the expandable system.

The compliance of the system may be varied by any combination ofmaterial selection, wall thickness, or length of the over-tube 258.Over-tube 258 may comprise any elastomer, such as elastic polymer likeNylon, Pebax, or PET. Typically, compliance tube 258 is formed fromextruded tubing, but it may also comprise braided polymeric or metallicfibers, or wire mesh. A high memory metal such as nitinol or stainlesssteel may also be used. Where the compliance tube comprises an extrudedpolymeric tube, the wall thickness can vary in the ranges set forthabove, and the length of the tube can range from 1 cm to 10 cm. For thesame material, the thinner-walled and longer the tube, the morecompliant the system.

Referring to FIGS. 18a-c , the compliance of angioplasty catheter 300may also be varied by creating one or more perforations in compliancetube 258. The perforations may comprise one or more slots in thecircumference of the tubing. The slots may comprise one continuous slotspiraling across the length of compliance tube 258, or may be a numberof slots aligned in any number of patterns, such as helical 312 orradial 314. The slots may also be any number of shapes, such as circularor rectangular, and may have a discreet length or be contiguous acrossthe surface of the compliance tube.

Referring to FIG. 19, the outside diameter of compliance tube 258 may betapered to facilitate delivery and retrieval of the scoring catheter 320from the treatment site within the lumen. Generally, the outer diameterwill be larger at the distal end 264 of the compliance tube 258 andsmaller at the proximal end 266 of the compliance tube. The outsidediameter D₁ at the distal end will vary depending on the profile of thescoring structure and balloon when collapsed but typically range from0.004 in. to 0.01 in. larger than the outside diameter D₂ at theproximal end. The outside diameter D₂ at the proximal end is generallyas close as possible to the outside diameter of the catheter body tocreate a smooth transition between the compliance tube and the catheter.As an example, for a catheter body having an outside diameter of 0.033in., outside diameter Di at the distal end may be 0.042 in. with aninner diameter of 0.038 in., the inner diameter providing clearancebetween the catheter body so that the distal end of the compliance tubecan move relative to the catheter body. Correspondingly, the outsidediameter D₂ at the proximal end may taper down to 0.0345 in., with aninner diameter of 0.034 in. to closely match the catheter body havingoutside diameter with enough clearance to be bonded to the catheter bodyby an adhesive.

The taper may run across the whole length of the compliance tube, oralternatively be only tapered at a section of the length of thecompliance tube. The tapered compliance tube 258 smoothes the transitionbetween the scoring structure and catheter body, and minimizes thelikelihood of the outer tube or scoring structure snagging or catchingon a portion of the luminal wall during delivery or retrieval of thecatheter.

Now referring to FIG. 20, an alternative embodiment of a scoringcatheter 350 is shown having a manipulator 360. The attachment structure258 is connected at its distal end 264 to the scoring structure 252.Instead of being secured directly to the catheter body 256, the proximalend 266 is attached to manipulator 360. Typically, the manipulator 360is positioned at the proximal end of the catheter body 256 and theattachment structure 258 extends from the scoring structure across thelength of the catheter body. Like the above embodiments, the attachmentstructure is capable of axially and rotationally extending toaccommodate foreshortening of the scoring structure as the shell isexpanded.

In some embodiments, the compliance of the scoring structure 252 andballoon 254 is controlled by actuating the manipulator during expansionor contraction of the radially expandable shell. In one aspect, theattachment structure 258 may be axially advanced with respect to thecatheter body 256 as the balloon is being inflated or deflated. Forexample, the attachment structure 258 may be pulled away from the distalend of the catheter body 256 while the balloon 254 is being expanded toconstrain the compliance of balloon. The attachment structure 258 mayalso be pulled away from the distal end of the catheter body 256 duringor after the balloon 254 is being deflated to minimize the profile ofthe balloon and scoring structure. Alternatively, the manipulator 360may be used to rotate the attachment structure 258 with respect to thecatheter body 256 to control the compliance of the balloon and scoringstructure during transition from a collapsed to expanded state and backto a collapsed state.

Now referring to FIGS. 21 and 22, a scoring cage structure 400 isillustrated having a two-layer laminated compliance tube 402. As shownin FIG. 22, the compliance tube 402 has a laminated structure 404 at atleast its distal end 410. The laminated structure holds the proximalends 408 of the scoring elements 406 as shown in broken line in FIG. 22.The scoring elements 406 may be sized to fit over the outside of thecompliance tube 402, as illustrated in FIG. 22, with the laminationcovering the elements. Alternatively, the compliance sleeve tube 402 maybe sized to fit inside of the scoring structure 406, with the laminatinglayer(s) formed over the elements 406 (not shown).

The laminating structure may be composed of a polymer similar to thecompliance tube 402, and may be heat shrunk or melted to thermally bondthe compliance sleeve to the compliance tube and sandwich the scoringstructure 406. Alternatively, an adhesive or other bonding method suchas ultrasonic or RF energy may be used to laminate the structure. Thelaminated structure, as shown in FIGS. 21 and 22, provides a smoothedtransition and strengthened bond between the scoring cage and theattachment structure. Such a smooth transition is a particular advantagewhen withdrawing the scoring cage from the vasculature.

FIGS. 23 and 24 illustrate scoring cage 400 positioned over anexpandable dilation balloon 412. As shown in FIG. 24, distal end 418 ofthe scoring structure may be coupled to the distal tip 414 of thecatheter body by an end cap 416. The end cap 416 may be composed of acompatible polymer and thermally bonded with the catheter body to fixdistal end 418 of the scoring structure to the catheter body.

Now referring to FIGS. 25-27, a method is illustrated for mounting anexpandable scoring cage 406 over a balloon catheter. The scoring cage406 is pre-expanded by loading it over an insertion tube 422 that has aninner diameter slightly larger than the outer diameter of the balloon412. A catheter body 420 having a balloon 412 is then inserted into theinner diameter of the insertion tube 422 and advanced until the balloon412 is appropriately positioned with respect to the scoring structure406, as illustrated in FIG. 26. The insertion tube 422 is then pulledback to allow the expanded scoring structure to collapse over theballoon 412 and the catheter body 420, as shown in FIG. 27. The scoringstructure 406 may then be secured at its distal end 418 to the distaltip 414 of the catheter body 420 and the proximal end 424 of the scoringstructure/attachment structure assembly to a medial location on thecatheter body 420.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Alternate embodiments are contemplated that fallwithin the scope of the invention.

What is claimed is:
 1. A scoring catheter comprising: a catheter bodyhaving a proximal portion and a distal portion; a radially expansibleshell disposed adjacent the distal portion of the catheter body, whereinthe radially expansible shell carries a drug; and a non-axial scoringcage disposed over the radially expansible shell, wherein the non-axialscoring cage is unattached to the radially expansible shell, wherein thenon-axial scoring cage includes a plurality of helical scoring elementscircumscribe the radially expansible shell, wherein the helical scoringelements are elastic, whereupon radial expansion and collapse of theradially expansible shell, the helical scoring elements expand andcollapse while remaining over the radially expansible shell.
 2. Thescoring catheter of claim 1, wherein the radially expansible shell is aballoon.
 3. The scoring catheter of claim 1, wherein the radiallyexpansible shell has an expansible area and the non-axial scoring cagecovers a percentage of the expansible area less than or equal to 20%. 4.The scoring catheter of claim 1, wherein the non-axial scoring cagecomprises a laser-cut hypotube.
 5. The scoring catheter of claim 1,wherein the non-axial scoring cage comprises a first end and a secondend, wherein the first end is axially fixed to the catheter body and thesecond end is unattached to the catheter body and able to free to slideaxially.
 6. The scoring catheter of claim 1, wherein the non-axialscoring cage comprises a first attachment structure and a secondattachment structure, wherein the helical scoring elements are disposedbetween the first attachment structure and the second attachmentstructure.
 7. The scoring catheter of claim 6, wherein the firstattachment structure is fixed to the catheter body on one side of theradially expansible shell.
 8. The scoring catheter of claim 1, furthercomprising an attachment element attaching the non-axial scoring cage tothe catheter body, wherein the attachment element is a cylindrical tubecircumscribing the catheter body.
 9. The scoring catheter of claim 8,wherein the attachment element floats over the catheter body.
 10. Thescoring catheter of claim 8, wherein the attachment element is fixed tothe catheter body.
 11. A scoring catheter comprising: a catheter bodyhaving a proximal portion and a distal portion; a radially expansibleshell disposed adjacent the distal portion of the catheter body, whereinthe radially expansible shell carries a drug; and an elastic scoringcage comprising a plurality of scoring elements circumscribing theradially expansible shell, wherein the elastic scoring cage has a freeend and a fixed end, wherein the fixed end is axially fixed to thecatheter body, wherein the free end slides axially as the radiallyexpansible shell expands radially, wherein the elastic scoring cageremains over the radially expansible shell as the radially expansibleshell expands and collapses.
 12. The scoring catheter of claim 11,wherein at least a portion of the elastic scoring cage is non-axiallyaligned over the radially expansible shell.
 13. The scoring catheter ofclaim 11, wherein at least a portion of the elastic scoring cage ishelically over the radially expansible shell.
 14. The scoring catheterof claim 11, wherein at least a portion of the elastic scoring cagecomprises a wire.
 15. The scoring catheter of claim 11, wherein theelastic scoring cage comprises a first attachment structure and a secondattachment structure, wherein the scoring elements are disposed betweenthe first attachment structure and the second attachment structure,wherein only the first attachment structure is fixed and the secondattached structure is adapted to axially slide as the scoring elementforeshortens as the radially expansible shell is expanded.
 16. Thescoring catheter of claim 15, wherein the first attachment structures isfixed to the catheter body on one side of the radially expansible shell.17. The scoring catheter of claim 15, wherein the second attachmentstructure includes an axially extensible component adapted toaccommodate foreshortening of the scoring element as the radiallyexpansible shell expands.
 18. The scoring catheter of claim 11, furthercomprising an attachment element attaching the elastic scoring cage tothe catheter body, wherein the attachment element is a cylindrical tubecircumscribing the catheter body.
 19. The scoring catheter of claim 18,wherein the attachment element floats over the catheter body.
 20. Thescoring catheter of claim 18, wherein the attachment element is fixed tothe catheter body.